Luz Araceli Ochoa-Martínez

Effect of high-pressure homogenization on the physical and antioxidant properties of Quercus resinosa infusions encapsulated by spray-drying.

Quercus resinosa leaves are used in northern Mexico as a refreshing beverage rich in polyphenolic compounds. These leaves show astringency and hence need taste masking for incorporating in a food product. They also interact with many other food components and are not very stable to food processing environments, thus it is important to protect them and a common way is by encapsulation. In the present study the use of encapsulation by spray-drying of Quercus resinosa leaves infusions was evaluated. Q. resinosa leaves were collected, air dried, and milled prior to infusion preparation. Lactose-sodium caseinate blends at 3 different proportions (11 : 4%, 9 : 6%, and 7 : 8%) were dispersed with a constant amount of lyophilized infusion (0.075%) and processed under high-pressure homogenization (0, 100, 200, 300 MPa). Total phenolic content, DPPH kinetic analysis, deoxy-D-ribose oxidation inhibition, rheological evaluation, and particle size analysis were performed to evaluate the obtained capsules. High antioxidant activity was shown by capsules despite their very low concentration when inhibiting deoxy-D-ribose oxidation. Chain breaking rate was related to polyphenolic concentration in capsules. Using lactose-caseinate blends produces capsules of submicron to nanometer size that retain the good antioxidant capacities of original infusions.

Effect of pre-treatment on physicochemical and structural properties, and the bioaccessibility of β-carotene in sweet potato flour

The aim of this research was to evaluate the effect of microwave or steam pre-treatment of raw sweet potato on physicochemical and microstructural properties, and the bioaccessibility of β-carotene in sweet potato flour. This is the first report on using the in vitro digestion model suitable for food, as proposed in a consensus paper, to assess the bioaccessibility of β-carotene in sweet potato flour. The pre-treatments produced a rearrangement of the flour matrix (starch, protein and non-starch polysaccharides), which was greater by using microwaves (M6) conducting to a greater increase in the phase transition temperatures up to 4.14 °C, while the enthalpy presented the higher reduction (4.49 J/g), both parameters in respect to the control. The resistant starch fraction was not modified, with about 3% in all samples. Microwave (M6) and all the steam pre-treatments showed the higher bioaccessibility of β-carotene. This flour can be used in the development of new products with high β-carotene content.

Efecto de la aplicación de alta presion hidrostática sobre la inactivación microbiana y las propiedades fisicoquímicas de arilos de granada

El objetivo de este trabajo fue evaluar el efecto de la APH sobre la vida útil microbiológica y parámetros físico-químicos (pH, acidez, actividad antioxidante, contenido de polifenoles, SST y color) de arilos de granada durante su almacenamiento a temperatura de refrigeración. Se aplicaron tratamientos de 350, 450 y 550 MPa durante 30, 60 y 90 s, posteriormente las muestras se almacenaron a 4°C durante 35 días. Las muestras fueron sometidas a recuentos microbianos y análisis físico-químicos. Todos los tratamientos de APH ensayados lograron reducir la carga microbiana inicial (1,0 y 1,6 log UFC/g) a <1,0 log UFC/g. La vida útil se logró extender a más de 35 días, independientemente del tratamiento aplicado. El contenido de polifenoles totales y la actividad antioxidante de las muestras procesadas disminuyeron significativamente (p < 0,05) durante el tiempo de almacenamiento en comparación con la muestra control.

Mixing and tempering effect on the rheological and particle size properties of dark chocolate coatings Efecto del mezclado y temperado sobre las propiedades reológicas y de tamaño de partícula de coberturas de chocolate oscuro

Chocolate coatings are semisolid suspensions of fine particles from sugar, cocoa, non fat milk solids in an oily phase. Processing steps of chocolate include mixing, refining, conching, tempering, molding, and packing. Tempering is a directed pre-crystallization that consists of shearing chocolate mass at controlled temperatures. The effect of mixing and tempering process on the particle size distribution and rheological behavior of dark chocolate coatings were evaluated. Each sample was melted (65 °C, 15 min) and tempered following three different procedures usually recommended for chocolate. Proximate composition analysis, specific surface area, mean particle diameter, consistency index (K), flow index (n), G′, G″ and electron micrographs (4000×) were obtained. All samples followed Casson flow model and (n) showed a pseudoplastic behavior. Higher values of K were shown by tempering process 3. Shear increased chocolate storage module (G′) and its stability. Samples without tempering and shearing have shown higher values of particle size. Las coberturas de chocolate son suspensiones semi-sólidas de partículas pequeñas de azúcar, cacao, sólidos no grasos de leche en una fase oleosa. Los pasos del procesamiento de chocolate incluyen mezclado, refinación, conchado, temperado, moldeo y empacado. El temperado es una pre-cristalización directa que consiste en cizallar la masa de chocolate a temperaturas controladas. Se evaluó el efecto del mezclado y del temperado sobre la distribución del tamaño de partícula y el comportamiento reológico de coberturas de chocolate obscuro. Las muestras fueron fundidas (65 °C, 15 min) y temperadas siguiendo tres procedimientos recomendados. Se determinaron el análisis proximal, área superficial específica, diámetro medio de partícula, índice de consistencia (K), índice de flujo (n), módulos viscoelásticos (G′ y G″), y se usó micrografía electrónica, SEM (4000×). Todas las muestras presentaron un comportamiento al flujo ajustado al modelo de Casson. Los cambios de K estuvieron en función del proceso de temperado usado, pero (n) mostró cambios en su comportamiento pseudoplástico. Los mayores valores de K se obtuvieron para el temperado 3 y los menores para el temperado 1. El corte incrementó el módulo de almacenamiento (G′) y en consecuencia su estabilidad. Las muestras sin temperado y corte mostraron el mayor tamaño de partícula (9.17 μm).

Husk Tomato (Physalis ixocarpa Brot.) Waste as a Promising Source of Pectin: Extraction and Physicochemical Characterization

Husk tomato (Physalis ixocarpa Brot. var. Rendidora) waste was evaluated as a source of specialized pectin, and pectin extracted from this waste was characterized physicochemically. Fruit was blanched for 10 or 15 min and extracted in 0.1 N HCl for 15 to 25 min. Extracted pectin was subjected to physicochemical analysis. For all extraction conditions, the percentage of anhydrogalacturonic acid exceeded 60%, indicating that husk tomato was a good source of pectin. The degree of esterification of pectin molecules was 63% to 91%. The amount of extracted pectin decreased with increasing extraction time. The apparent viscosity of husk tomato pectin showed the characteristic behavior of pseudoplastic fluids. Neutral sugars were identified, and the amounts of 6 sugars (fucose, rhamnose, arabinose, galactose, glucose, and xylose) were quantified. Sugars identified in husk tomato pectin and present in the Rhamnogalacturonan I region, arabinose, galactose, and rhamnose suggest a highly branched structure, which will influence its future applications. Molecular weight values were 542 to 699 kDa, exceeding molecular weight values reported for commercial citrus pectins from 134 to 480 kDa. The extraction process significantly (P < 0.05) influenced the physicochemical properties of pectin. Up to 19.8% from the total amount of pectin in the husk tomato was extracted by 10 min of blanching and 20 min of a more heat treatment. Our findings indicate that husk tomato can be a good alternative source of pectin having highly distinctive physicochemical characteristics.

Conjugated linoleic acid content in selected Mexican beef and dairy products

The purpose of this study was to assess the conjugated linoleic acid (CLA) content of some commercial beef cuts and dairy products. Levels of CLA ranged between 3.75 and 20.45 mg/g fat, corresponding to 2% milk and cooked ground beef. On the basis of serving size, CLA content ranged between 12.87 and 93.62 mg/portion, corresponding to cream cheese (portion of 15 g) and cooked ground beef (portion of 100 g). There was no direct relationship between CLA content and the amount of fat provided per serving size in dairy foods. This study showed the presence of significant amounts of natural CLA in beef and dairy fats in the foods analyzed.

Effect of nixtamalization conditions ultrasound assisted on some physicochemical, structural and quality characteristics in maize used for pozole

Traditional nixtamalization (TN) and assisted ultrasound nixtamalization (ASN) were carried out on maize kernel (Zea mays) used for pozole elaboration, evaluating some physicochemical, structural and quality characteristics. It was found that the cooking time for popping (CTP) varied from 92 to 99 min in TN samples and from 72 to 90 min in ASN samples. The percentage of popped grains and the expansion volume did not show significant differences between treatments. In general, it was observed more luminous color and a lower b* value, which indicate the yellow color when sonication was used during the nixtamalization process. Less starch damage was observed when sonication was applied during the nixtamalization process. Using the ASN, up to 20 min in the CTP was reduced for obtaining the maize kernel for pozole.

Blue corn (Zea mays L.) with added orange (Citrus sinensis) fruit bagasse: novel ingredients for extruded snacks

Physicochemical and structural analyses were done of extruded snacks produced with two types of blue corn (hard and soft endosperm) combined with orange bagasse. Chemical composition, expansion index (EI), penetration force, water absorption index, and water solubility index values were calculated for all treatments. They were also analyzed with scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Addition of bagasse increased crude fiber content and hardness in the extrudates. It also lowered the EI, resulting in harder products with higher numbers of pores per area but of smaller sizes than in the extrudates without bagasse. Both the X-ray diffraction patterns and infrared spectra showed the starch to lose its semicrystalline structure due to mechanical shearing and high temperature. Orange bagasse was successfully incorporated into extrudated snacks made with blue corn of different endosperm hardnesses. Blue corn is a viable base for extruded snacks, and orange bagasse is a potential source of low cost, natural source fiber.

Quality evaluation of tortilla chips made with corn meal dough and cooked bean flour

Abstract A mixture of cornmeal dough and cooked bean flour (BF) was prepared at different ratios (50/50, 60/40, and 70/30 w/w), and processed to chips. Viscosity profile, temperature of gelatinization and enthalpy, texture, protein content, and in vitro digestibility were measured. Pasting temperature tended to be lower when the flour bean concentration was lower. Maximum viscosity increased significantly in both samples (dough mixture and chips) when the BF concentration was lower. In general, gelatinization temperature remains constant, while the heating enthalpy was higher with lower BF concentration. The addition of BF was correlated with greater crispiness, suggesting improved chip texture at higher BF concentrations. The final protein content in the corn-bean chips was very similar, despite the concentration of BF used. Protein digestibility in the chips was affected by the proportion of BF added, being higher when the amount of the BF was lower.

MATHEMATICAL MODEL FOR PREDICTION OF MOISTURE CONTENT IN JALAPEÑO PEPPER (Capsicum frutescens) MODELO MATEMÁTICO PARA LA PREDICCIÓN DEL CONTENIDO DE HUMEDAD EN CHILE JALAPEÑO (Capsicum frutescens) MODELO MATEMÁTICO PARA A PREDICCIÓN DO CONTIDO DE HUMIDADE EN CHILE JALAPEÑO (Capsicum frutescens)

Abstract A model to predict the moisture content in jalapeño peppers (Capsicum frutescens) has been presented. The product was dried under five drying temperatures (50, 60, 70, 80 and 95°C), and these experiments provided data for model formulation. Analysis of the simulated results have indicated that there are two possible mechanisms for jalapeño peppers drying, both of which are a function of the temperature. It was found that one mechanism occurs below 60°C and the other at temperature above 80°C.